This is an Owden Edge Creaser in the 2.5mm size.
Heated over a gas flame, a creasing iron is used to make a neat decorative line along the edges of your leather and can be used on everything from belts and dog collars to bookbinding projects.
Carefully engineered from stainless steel, this crease tool has an ebony handle and brass ferrule.
This tool is designed for right handed use. You can also use it in your left hand, but the resulting line will be nearer to the edge of your leather.